Western Indian Ocean JOURNAL OF Marine Science

Volume 15 | Issue 2 | Jul – Dec 2016 | ISSN: 0856-860X Chief Editor José Paula Western Indian Ocean JOURNAL OF Marine Science

Chief Editor José Paula | Faculty of Sciences of University of Lisbon, Portugal Copy Editor Timothy Andrew

Editorial Board Louis CELLIERS Blandina LUGENDO South Africa Lena GIPPERTH Aviti MMOCHI Serge ANDREFOUËT Sweden Tanzania France Johan GROENEVELD Nyawira MUTHIGA Ranjeet BHAGOOLI South Africa Kenya Mauritius Issufo HALO Brent NEWMAN South Africa/Mozambique South Africa Salomão BANDEIRA Mozambique Christina HICKS Jan ROBINSON Australia/UK Seycheles Betsy Anne BEYMER-FARRIS Johnson KITHEKA Sérgio ROSENDO USA/Norway Kenya Portugal Jared BOSIRE Kassim KULINDWA Melita SAMOILYS Kenya Tanzania Kenya Atanásio BRITO Thierry LAVITRA Max TROELL Mozambique Madagascar Sweden

Published biannually Aims and scope: The Western Indian Ocean Journal of Marine Science provides an avenue for the wide dissem- ination of high quality research generated in the Western Indian Ocean (WIO) region, in particular on the sustainable use of coastal and marine resources. This is central to the goal of supporting and promoting sustainable coastal development in the region, as well as contributing to the global base of marine science. The journal publishes original research articles dealing with all aspects of marine science and coastal manage- ment. Topics include, but are not limited to: theoretical studies, oceanography, marine biology and ecology, fisheries, recovery and restoration processes, legal and institutional frameworks, and interactions/relationships between humans and the coastal and marine environment. In addition, Western Indian Ocean Journal of Marine Science features state-of-the-art review articles and short communications. The journal will, from time to time, consist of special issues on major events or important thematic issues. Submitted articles are subjected to standard peer-review prior to publication. Manuscript submissions should be preferably made via the African Journals Online (AJOL) submission plat- form (http://www.ajol.info/index.php/wiojms/about/submissions). Any queries and further editorial corre- spondence should be sent by e-mail to the Chief Editor, [email protected]. Details concerning the preparation and submission of articles can be found in each issue and at http://www.wiomsa.org/wio-journal-of-marine- science/ and AJOL site. Disclaimer: Statements in the Journal reflect the views of the authors, and not necessarily those of WIOMSA, the editors or publisher.

Copyright © 2016 —Western Indian Ocean Marine Science Association (WIOMSA) No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means without permission in writing from the copyright holder. ISSN 0856-860X

Cover image: A seagrass meadow (Thalassia hemprichii) at Inhaca Island, Mozambique (© José Paula, 2017) WIO Journal of Marine Science 15 (2 ) 2016 67-74 Original Article 67

Effect of Stocking Density on Growth Performance of Hybrids of Oreochromis niloticus♀ and Oreochromis urolepis urolepis♂ in Saline Water

Levinus L. Mapenzi1, 2, Aviti J. Mmochi2

1 Department of Biotechnology 2 Institute of Marine Sciences, * Corresponding author: and Bioinformatics, University University of Dar es Salaam, P.O. [email protected] of Dodoma, P.O. Box 338, Box 668, Zanzibar, Tanzania Dodoma, Tanzania

Abstract Fingerlings of Oreochromis niloticus♀ and Oreochromis urolepis urolepis♂ hybrids were reared at stocking densities of control, 5, 10, 15 and 20 fish/m3 at 15 Practical Salinity Units (PSU) in 1m3 plastic tanks for 63 days. They were kept at low, intermediate and high densities respectively. All hybrids were fed on a formulated, balanced diet consisting of 40% crude protein, at a ratio of 5% body weight, twice daily. Low stocking density showed better growth perfor- mance in terms of mean weight gain, specific growth rate (SGR), feed conversion ratio (FCR) and survival rate, than intermediate and high stocking densities. SGR, FCR and survival rates did not vary significantly between treatments (p>0.05). Average final weight gain was significantly different between intermediate and high densities (p<0.05), high and low densities, but not in low and intermediate densities. Density was found to have an effect on the growth of the juvenile hybrids, since higher growth was recorded at low stocking densities compared to the intermediate and high densities. Hybrids were 100% male when inspected. The low and intermediate densities are therefore recommended for hybrids aquaculture in brackish water with the latter being suggested due to its higher yield compared to the low stocking density.

Keywords: Hybridization, all male hybrids, stocking density, growth performance, hybrids.

Introduction were not 100% males. Mtaki (2015) successfully pro- Orochromis niloticus L. is a widely cultured fish species duced 100% males when hybridizing O. niloticus♀ and in Tanzania. However, the species reproduces pro- O. urolepis urolepis♂ but did not test the influence of lifically in captivity in mixed-sex culture. Its -uncon stocking density on such hybrids. Hybridization was trolled propagation leads to overcrowding, stunted aimed at producing male tilapia with good growth and growth, and competition for food (Mensah et al., 2013) salinity tolerance traits inherited from both O. niloti- and space. The resulting early maturity and stunted cus and O. urolepis urolepis parents. In order to better growth lead to unmarketable fish size problems at understand their value for aquaculture, the influence harvest (Mensah et al., 2013). To improve performance of stocking densities on growth and yield needed to of O. niloticus, efforts have been made to produce all be determined. male (mono-sex) fish populations using various tech- niques. These include production of hormonally Stocking density is defined as the number of fish per reversed males, hybridization of O. niloticus♀ and unit area or volume. It determines fish health (Garr O. urolepis hornorum♂ (Mbiru et al., 2016) and manual et al., 2011), growth, survival and yield (Khatune-Jan- sexing (Guerrero, 1982). Males have bigger body sizes nat et al., 2012; Rahman and Rahman, 2003). Suita- and grow faster, with more uniform size, in relation to ble stocking density varies with species, water quality females (Celik et al., 2011). Hybrids of O. niloticus♀ and and feeding regimes, and is important for sustain- O. urolepis hornorum♂ were found to have high growth able aquaculture (Russell et al., 2008). Higher stock- performance in freshwater (Mbiru et al., 2016) but ing densities may increase fish yield (Khatune-Jannat 68 WIO Journal of Marine Science 15 (2 ) 2016 67-74 | L. Mapenzi & A. Mmochi

et al., 2012), lower production costs and increase profit (2012) noted that appropriate stocking density is a key (Abou et al., 2007). Ridha (2005) recommended high to minimizing tilapia production problems, and rec- stocking densities in places with limited land, fresh ommended a stocking density of 5 fish/m3 for better water and man power. However, higher stocking growth performance of improved strains of Oreochro- densities may adversely affect growth performance mis shiranus. According to Alhassan et al. (2012), stocking and survival (Sorphea et al., 2010; Pouey et al., 2011). density governs the economic viability of the produc- For example, higher growth and survival rates were tion system. In this regard, determining the optimum documented at lower stocking densities for Oreo- stocking density of the hybrids from natural hybridi- chromis species (Sorphea et al., 2010), and Ronald zation of O. niloticus♀ and O. urolepis uroelpis♂ is crucial. et al. (2014) observed low survival rate at high stocking Aquaculture of saline-tolerant tilapia species is vital density of O. niloticus fry in ponds. In addition, high for coastal aquaculture improvement, provision of stocking density promotes competition for food and alternative employment and a reliable protein source. reduces fish reproductive success. The aim of this study was to produce fast growing and salinity tolerant all-male tilapia hybrids, and to rear Recommended stocking densities for tilapia culture them at different stocking densities to improve coastal differ extensively (Russell et al., 2008). Mb'alaka et al., aquaculture by promoting hybrid mariculture practices.

Figure 1. Map showing broodstock collection (Rufiji River) and the experimental (Bweni Village) sites. L. Mapenzi & A. Mmochi | WIO Journal of Marine Science 15 (2 ) 2016 67-74 69

Methodology hand-held marine tester (DMT-10) and a dissolved Study area oxygen meter (PDO-520), respectively. Hybrids with This study was conducted at the Institute of Marine average weights of 0.29±0.01g, 0.29±0.01g, 0.27±0.01g Sciences Mariculture Centre (IMS-MC) located at and 0.28±0.01g were stocked at 5, 10, 15 and 20 fish/ Bweni Village, District in m3, respectively. These were described as control, (05° 26´ 0˝ South, 38° 58´ 0˝ East, on the north east coast low, intermediate and high stocking densities accord- of Tanzania (Figure 1). The local communities’ eco- ingly. A 40% crude protein (CP) basal diet containing nomic activities involve fishing, seaweed farming and 48% maize flour, 3% cassava flour, 3% vitamins (Premix subsistence terrestrial agriculture. The area is drained for broilers), 6% sunflower seed cake, 7% shrimp meal, by the , whose basin starts from Kiliman- and 33% sardine meal was formulated and used to jaro and Meru mountains and the Pare and Usambara feed the hybrids. The formulation aimed at synchro- mountain ranges. It is well endowed with several types nizing spawning, and rapid growth. Fresh sardine and of terrestrial and marine ecosystems, including man- shrimp for fish meal were obtained from local fisher grove forests, which provide habitat for several marine folk. They were sun dried and milled prior to mixing and estuarine species. The Pangani River has a diversity with other ingredients. A meat mincer machine was of tilapia species which include O. korogwe, O. pangani, used in preparing the food pellets. Fish were fed at 5% O. variabilis, T. rendalli and T. zillii in the lower Pangani body weight, two times a day at 2.5% body weight at basin (Dallas et al., 2006). Pangani District is character- each feeding. Feeding was adjusted during the exper- ized by an annual rainfall of above 1000 mm with tem- iment as fish biomass per density changed with fish peratures varying between 22 °C and 30 °C a generally growth. Five individuals per tank were sampled every warm and humid climate. (Pamba et al., 2016). two weeks. The individual total weights were weighed using a digital balance. Measurements were done after Hybrid production removing excess water with tissue paper. The hybrids The O. niloticus and O. urolepis urolepis brooders were were not fed for 24 hours prior to sampling. To con- obtained from Lake Victoria, Mwanza and the Rufiji trol water quality, 20% of the water in the tanks was River respectively. They were raised in concrete tanks replaced once a week. Siphoning was done twice a at IMS-MC. They were morphologically identified week to remove uneaten food and faeces from the according to Eccles (1992) before being mated. Prior bottom of tanks. Uneaten food and faeces were dried, to stocking, the females’ mouths were inspected to weighed and subtracted from the amount fed, to remove any spawned eggs before pairing with males. obtain the FCR. The experiment was conducted for O. niloticus♀ and O. urolepis urolepis♂ of average weights 63 days from 2nd October to 5th December, 2015. The 68.6 ± 0.2g and 75.1 ± 0.3g respectively, were naturally hybrids were confirmed to be 100% males by external mated in plastic tanks. Brooders were deployed in visual examination and internally through dissection a 2:1 female to male ratio in 10 plastic tanks, each tank and gonadal inspection. The hybrids were then raised having a volume of 1m3. The brooders were fed with for nine months without showing any breeding signs. a 40% crude protein formulated diet. In addition, stones were placed in the tanks to serve as nests to assist with Determination of Growth Performance conditioning the fish to spawn. Growth performance in the studied hybrids was determined using the following indices: Experimental setup ln Wf- ln Wi An experiment with four levels of stocking density Specific Growth Rate (% day-1) = x 100…..…..1 [ T ] was conducted. The experiment was replicated three Total feed intake by fish (g) times, making a total of 12 tanks. A total of 150 hybrid Food Conversion Ratio (FCR) = ...... 2 Total weight gain by fish (g) fingerlings were randomly distributed in the experi- mental tanks containing water of 15 PSU. The hybrids Weight Gain (g) = Wf – Wi ………...... …………………………..3 were batch-weighed prior to stocking. Acclimation to Survival Rate (%) = Nf x 100……….……………...……………....4 15 PSU was done by gradually adding 2 PSU per day [ Ni ] for 8 days to each tank prior to experimental start-up. Water quality parameters were measured twice a day Where, T is the number of days of the experiment, throughout the experiment. PH and temperature were and Nf, Ni are the numbers of harvested and stocked measured using a HI8424 pH meter, while salinity and fish, i W and Wf are the initial and final mean body dissolved oxygen (DO) were measured by a digital weights, respectively. 70 WIO Journal of Marine Science 15 (2 ) 2016 67-74 | L. Mapenzi & A. Mmochi

The coefficient of condition W …………………….....…………....5 density treatments, including the 5 fish/m3 control L3 density. FCR was lower in the 10 fish/m3 than in the Where W = Weight of individual fish (g), L = Total 15 and 20 fish/m3 densities. However, all these param- length of individual fish, and K = condition factor eters did not vary significantly between treatments Length weight relationship was calculated as W = a Lb ...6 (p > 0.05, Table 2). On the other hand, the final mean which was transformed into common logarithm as weight of the fish did show a significant difference log W=log a+b.log L ...... 7 between treatments (p < 0.05, Table 3), with the 10 fish/ Where W = Weight of fish in gram (g), L = Total length m3 density treatment being higher than the control, of fish in centimeters (cm), a = proportionality - con 15 and 20 fish/m3 densities (Figure 2). The average ini- stant, b = the value obtained from the length-weight tial weights of fish, though it varied slightly, did not equation/coefficient of regression. differ significantly among treatments (p < 0.05, Table 2). Survival rate was managed by lowering the tanks’ Statistical Analysis water and counting all fish at sampling. No replace- Results are presented as mean ± standard error of the ment was done to maintain the fish density in tanks. means (SE). The within-treatment replicas were tested for significant differences, and were found to be insig- Length-weight Relationship (LWR) nificant at the 95% confidence level. Therefore, the and Condition Factor (K) within-treatment growth data were pooled for each Studies of length-weight relationship indicate fish treatment and tested for normality using Kolmogor- wellbeing and the effects of the environment on fish nov–Smirnov. The data were tested for homoscedastic- (Mansor et al. 2012). Where the regression coefficient ity with Levene’s test in Statistica 10 software. The data “b” value in a simple regression equation is greater, were found to be parametric and behaved homoscedas- less than, or equal to 3, the fish undergoes positive tically. Therefore, analysis was done following one way or negative allometric growth, and isometric growth analysis of variance (ANOVA). In the cases where a sta- respectively (Mansor et al. 2010). The condition factor tistical difference between means of stocking densities “K” reflects fish health and environmental suitability was found, a Tukey test was used to determine which (Mansor et al. 2012). particular means differed significantly from each other. In the present study the LWR “b” values were approx- Results imately 2.5, indicating negative allometric growth Water quality parameters (Table 3). The recorded “R2” values were 0.98, 0.97, Average water temperature ranged from 27-28.5ºC, 0.98 and 0.94 for control, low, intermediate and high dissolved oxygen from 5.8-6.5mg/L and pH from 7.0- stocking densities, respectively, which are similar. 7.9 units. All parameters revealed no significant differ- The correlation between length and weight was also ence between density treatments (p > 0.05, Table 1). significant (p < 0.05) in all densities, including the con- The parameters were within the acceptable range for trol. Moreover, the mean “K” value was about the same tilapia culture and fairly stable throughout the exper- for all treatments (Table, 3), and did not differ signifi- imental period. The parameters were measured twice cantly among treatments (p > 0.05). a day in the morning and evening. Discussion Stocking Densities Stocking density is very important for aquaculture as The 10 fish/m3 stocking density provided marginally it can influence fish yield and growth. In this study higher SGR, weight gain and survival rate than other positive growth occurred in all treatments. However,

Table 1: One way ANOVA results for water quality parameters between hybrid density treatments in tanks. (p > 0.05)

Density treatments Parameter 5 fish/m3(control) 10 fish/m3 15 fish/m3 20 fish/m3 p

Temperature 27.32±0.42 27.65±0.12 27.6 ±0.2 27.86 ±0.15 0.51

Dissolved oxygen 6.33 ±0.11 6.31 ±0.07 6.26 ±0.04 6.28 ±0.08 0.6

p H 7.69 ±0.07 7.68 ±0.09 7.75 ±0.09 7.77 ±0.08 0.84 L. Mapenzi & A. Mmochi | WIO Journal of Marine Science 15 (2 ) 2016 67-74 71

25

20

15 20 fish/m3 15 fish/m3 10 10 fish/m3 verage weights (g)

A 5 fish/m3 5

0 week 0 week2 week4 week6 week8

Figure 2. Increase in weight of the hybrids with time at different stocking densities, where week 0 refers .to the initial average weights measured.

the observed overlaps in growth may be due to man- for Figurefood and 2 space. High stocking density also reduces agement anomalies (Alhassan et al., 2012). For instance, water quality, resulting in poor fish health. Improved the 15 fish/m3 treatment showed a slight decline growth at low stocking density may therefore be attrib- in growth in week four. The low stocking density uted to favourable water quality factors (Osofero et al., (10 fish/m3) exhibited better growth in terms of weight 2009) and better feed quality. In this study, a balanced gain, SGR, FCR and survival rate, than intermediate diet for hybrids was prepared fortnightly using locally (15 fish/m3), high (20 fish/m3), and control stocking available feeds to ensure quality. All treatments had densities, respectively. However, none of these meas- better growth rates than the control. According to Yan ures were significantly different at the 95% confidence et al. (2002), low growth performances at very low den- level. The results are similar to Alhassan et al. (2012), sities are due to strong aggressive behaviour. Mbiru and Chakraborty and Banerjee (2010) who observed et al. (2016) described high growth rates in hybrids of reduced growth rates of O. niloticus at high stocking den- O. niloticus♀ and O. urolepis hornorum♂. The authors sities in concrete tanks and hapas in Ghana, and in all- stated that the high growth rates found were due to the male O. niloticus reared in ponds in the Gangetic plains effect of hybrid heterosis inherited from parents. of West Bengal, India, respectively. Reduced growth performance of hybrids at high stocking density may The survival rates were greater in low and intermedi- be due to extra energy expenditure on competition ate stocking densities than high and control stocking

Table 2. One way ANOVA results for growth performance indices of hybrids. Means without common superscripts in a row are significantly dif- ferent (p < 0.05,Tukey test).

Parameter 5 fish/m3(control) 10 fish/m3 15fish/m3 20 fish/m3 p

Initial mean weight(g) 0.29±0.5a 0.29±0.5a 0.27±0.5a 0.28±0.5a 0.31

Final mean weight (g) 20.14±6.66a 22.22±9.05ab 21.09±11.2ab 15.31±8.59ac 0.03

Yield (g) 362.52 1562.28 2642.4 4627.2 -

Weight gain 19.85±7.38a 21.93±7.47a 20.83±7.91a 15.03±5.45b 0.84

Survival rate (%) 90±12.2a 95±14.2a 92±12.37a 88±13.1a 0.25

FCR 1.35±2.34a 1.01±1.99a 2.30±5.06a 2.85±4.18a 0.2

SGR (%/day) 6.84±0.50a 8.33±0.60a 8.31±0.49a 7.8±0.60a 0.21 72 WIO Journal of Marine Science 15 (2 ) 2016 67-74 | L. Mapenzi & A. Mmochi

Table 3. Parameters for hybrids length-weight relationship at different density treatments.

Density L-W Relationship (fish/m3) a b R2 Mean K

Control -1.14 2.58 0.98 2.73 10 -1.15 2.51 0.97 2.83 15 -1.12 2.46 0.98 3.06 20 -1.11 2.48 0.94 3.11 densities, but not statistically significant. The results resulting in inappropriate dietary energy utiliza- agree with Chakraborty and Banerjee (2010), who tion due to physiological alterations, leading to poor documented an inverse relationship between high growth. The 1.01-2.85 FCR in this study was less than stocking density and fish survival. However, in this the 3.4-4.0 range recommended for O. niloticus (Liti study the maximum survival rate of 90% was above et al., 2006). However, the results fall within the recom- the 84.5% found by Chakraborty and Banerjee (2010), mended FCR for O. niloticus, a faster grower. and the 86.78% found by Alhassan et al. (2012). In addi- tion, acclimation, sampling method and tank clean- SGR values in this study are higher than the 0.77-1.49 ing mechanisms can account for lower survival rates. values reported for red tilapia by Iluyemi et al. (2010). In adapting fish to live in saline conditions, some The SGR values of 8.33, 8.3, and 7.8 are also higher were unable to withstand the harsh salty conditions than the 4.72 and 4.16 reported by Mtaki (2015) for and water mixing procedures and died. Scoop nets hybrids reared in concrete tanks. Besides the quality that were locally made of iron materials were noted of the feed used, heterosis for growth performance to cause injuries to fish during the sampling process inherited from both O. niloticus and O. urolepis urolepis and could lead to injury and later mortality. Similarly, parents may account for higher SGR in this study. siphoning using a plastic pipe may have caused deaths Weight gain and final mean weight were higher in in the tanks if fish were injured by the pipe, or by the low stocking density, corresponding to the results swimming into the tank walls in an attempt to evade of Ferdous et al. (2014). However, final mean weight the pipe. According to Ronald et al. (2014), high stock- varied significantly between intermediate and high ing density leads to high mortalities because of poor stocking density. water quality at densities above the carrying capacity of the culture unit. Condition factor describes fish health and fitness in the environment (Mbiru et al., 2016). The mean “K” values The ability of hybrids to convert food into biomass in this study were higher than the 1.02 and 1.12 reported (FCR) was not significantly affected by stocking density. for O. niloticus (Migiro et al., 2014), 0.53 for O. urolepis The best FCR was observed at the low stocking density, urolepis (Nehemia et al., 2011) and 1.71 for O. niloticus♀ implying better food utilization at low density. Current and O. urolepis hornorum♂ hybrids (Mbiru et al., 2016). findings correspond with those of other authors who The current findings concur with Mahomoud et al. documented non-significant FCR from monosex male (2011) who described higher “K” values in tilapia males; O. niloticus fry reared in hapas in ponds, and hybrids of which indicates good fish health (Froese, 2006). The O. mossambicus and O. niloticus, respectively, due to water present mean “K” values suggest an increase in hybrid quality factors, stress levels of fish and feed sources weight relative to length which indicates suitability of (Ferdous et al., 2014; Alhassan et al., 2012; Guimaraes the applied stocking densities for fish growth in tanks. et al., 2008, Yan et al., 2002). In this study hybrids were fed with the same basal feed and raised in water com- The hybrids of O. niloticus♀ and O. urolepis urolepis♂ ing from the same source. However, the FCR increased can be used as an alternative to hormonally reversed with stocking density, similar to the findings of Ferdous males for aquaculture, as hybridization produced et al. (2014) and Ronald et al. (2014). Common reasons 100% males. In addition, this study shows that farm- for poor FCR are stress, and high crude fibre content ers can potentially utilize the hybrids to obtain fish in diets (El-Sherif and El-Feky, 2009; Ali and Al-As- of market size earlier, because of their faster growth gall, 2001). El-Sherif and El-Feky (2009) reported that rates. The potential shown by this hybrid for aquacul- increased stress caused increased cortisol production ture needs to be investigated further in Tanzania. L. Mapenzi & A. Mmochi | WIO Journal of Marine Science 15 (2 ) 2016 67-74 73

Acknowledgements Garr AL, Lopez H, Pierce R, Davis M (2011) The effect of The authors appreciate the support provided by the stocking density and diet on the growth and survival Institute of Marine Sciences, Zanzibar, and through it, of cultured Florida apple snails, Pomacea paludosa. the Sida Marine Science Programme, for funding the Aquaculture 311: 139 –145 study, with partial support from the Commonwealth Guerrero RD, III (1982) Control of tilapia reproduc- Scientific Industrial Research Organization (CSIRO). tion. Pages 309–316 In: R.S.V. Pullin and R.H. Lowe McConnell, Eds. The Biology and Culture of Tila- References pias. ICLARM Conference Proceedings 7. Interna- Abou Y, Fiogbe ED, Micha JC (2007) Effects of stocking tional Center for Living Resources Management, density on growth, yield and profitability of farming Manila, Philippines Nile tilapia, Oreochromis niloticus L., fed Azolla diet, Guimaraes IG, Pezzato LE, Barros MM, Tachibana L in earthen ponds. Aquaculture Research 38: 595–604 (2008) Nutrient digestibility of cereal grain products Alhassan EH, Abarike ED, Ayisi CL (2012) Effects of stock- and by-products in extruded diets for Nile tilapia. ing density on the growth and survival of Oreochro- Journal of World Aquaculture Society 39: 781-789 mis niloticus cultured in hapas in a concrete tank. Hassan A (2011) Acclimatization, survival and growth rates African Journal of Agricultural Research 7: 2405-2411 of Pangani tilapia (Oreochromis pangani) in different Ali A, Al-Asgall NA (2001) Effect of feeding different car- salinities in Tanzania. Master of Science (Marine bohydrate to lipid ratios on the growth performance Sciences) thesis, University of Dar es Salaam. 65 pp and body composition of Nile tilapia (Oreochromis Iluyemi FB, Hanafi MM, Radziah O, Kamarudin MS niloticus) fingerlings. Animal Research 50: 91-100 (2010) Nutrition evaluation of fermented palm ker- Celik I, Guner Y, Celik P (2011) Effect of orally-adminis- nel cake using red tilapia. African Journal of Biotech- tered 17a-methyltestosterone at different doses on nology 9: 502-507 the sex reversal of the Nile tilapia (Oreochromis nilot- Khatune-Jannat M, Rahman MM, Bashar MA, Hasan MN, icus, Linneaus 1758). Journal of Animal Veterinary Ahamed F (2012) Effects of stocking density on sur- Advances 10: 853–857 vival, growth and production of Thai climbing perch Chakraborty SB, Banerjee S (2010) Effect of stocking den- (Anabas testudineus) under fed ponds. Sains Malaysi- sity on monosex nile tilapia growth during pond cul- ana 41: 1205–1210 ture in India. World Academy of Science, Engineer- Liti DM, Mugo RM, Munguti JM, Waidbacher H (2006) ing and Technology 68: 1511-1515 Growth and economic performance of Nile tilapia Dallas HF, Kamugisha S, Lugomela G, Mbaga J, Benno (Oreochromis niloticus L.) fed on three brans (maize, BL, Kaaya LT, Mbago FM, Materu E, Maggida A, wheat and rice) in fertilized ponds. Aquaculture King JM, Brown CA (2006) River Health Assessment. Nutrition 12: 239–245 IUCN Water and Nature Initiative, Pangani Basin Mahomoud WF, Amal MMA, Kamal FEA, Mohamed R, Water Office. UNDP, GEF. 185 pp Magdy MK (2011) Reproductive biology and some Eccles DH (1992) FAO Species Identification Sheets for observation on the age, growth, and management Fishery Purposes. Field Guide to the Freshwater of Tilapia zilli (Gerv, 1848) from Lake Timsah, Egypt. Fishes of Tanzania, United Nations Development International Journal of Fisheries and Aquaculture Programme, Project URT/87/016, FAO, Rome, Italy 3:15 –25

El-Sherif M, El-Feky MI (2009) Performance of Nile tila- Mansor MI, Basri MNA, Zawawi MI, Yahya K, Nor SAM pia (Oreochromis niloticus) fingerings effect. Philip- (2012) Length-weight relationships of some impor- pines International Journal of Agricultural Biology tant estuarine fish species from Merbok Estuary, 1: 297-300 Kedah. Journal of Natural Sciences Research 2: 2012

Ferdous Z, Masum MA, Ali MM (2014) Influence of stock- Mansor MI, Che-Salmah MR, Rosalina R, Shahrul-Anuar ing density on growth performance and survival of MS, Amir-Shah-Ruddin MS (2010) Length-weight monosex tilapia (Oreochromis niloticus) fry. Interna- relationships of freshwater fish species in Kerian tional Journal of Research in Fisheries and Aquacul- River Basin and Pedu Lake. Research Journal of ture 4: 99-103 Fisheries and Hydrobiology 5: 1-8

Froese R (2006) Cube law, condition factor and weight- Mbiru M, Limbu SM, Chenyambuga SW, Lamtane length relationships: history, meta-analysis and rec- HA, Tamatamah R, Madalla NA, Mwandya AW (2016) ommendations. Journal of Applied Ichthyology 22: Comparative performance of mixed-sex and hor- 241–253 monal-sex-reversed Nile Tilapia Oreochromis niloti- cus and Hybrids (Oreochromis niloticus × Oreochromis 74 WIO Journal of Marine Science 15 (2 ) 2016 67-74 | L. Mapenzi & A. Mmochi

urolepis hornorum) cultured in concrete tanks. Aqua- Pouey JL, Piedras SRN, Rocha CB, Tavares RA, Santos culture International 24: 557–566 JDM (2011) Productive performance of silver catfish, Rhamdia quelen, juveniles stocked at different densi- Mensah ET, Attipoe TK, Ashun-Johnson M (2013) Effect ties. ARS Veterinaria, 27: 239–245 of different stocking densities on growth perfor- mance and profitability of Oreochromis niloticus fry Rahman MR, Rahman MA (2003) Studies on the growth, reared in hapa-in-pond system. International Jour- survival and production of calbasu (Labeo calbaus nal of Fisheries and Aquaculture 5: 204-209 Ham.) at different stocking densities in primary Migiro KE, Ogello EO, Munguti JM (2014) The length- nursing. Bulletin Faculty of Science University of weight relationship and condition factor of Nile Ryuyus Japan 76: 245-255 Tilapia (Oreochromis niloticus L.) broodstock at Kegati Ridha MT (2005) Comparative study of growth perfor- Aquaculture Research Station, Kisii, Kenya. Interna- mance of three strains of nile tilapia, Oreochromis tional Journal of Advanced Research 2: 777-782 Niloticus, L. at two stocking densities. Aquaculture Mtaki K (2015) Growth and survival rate of Nile Tila- Research 37: 172–179 pia (Oreochromis Niloticus, Linnaeus 1958) females crossed with Rufiji Tilapia Oreochromis( urolepis uro- Ronald N, Gladys B, Gasper E (2014) The Effects of stock- lepis, Norman 1922) males hybrids reared at different ing density on the growth and survival of Nile tilapia salinities. Master of Science (Marine Sciences) thesis, (Oreochromis niloticus) fry at Son fish farm, Uganda. University of Dar es Salaam. 93 pp Journal of Aquaculture Research and Development 5: 1-7 Nehemia A, Maganira JD, Rumisha S (2012) Length-weight relationship and condition factor of tilapia species Russell AJM, Grotz PA, Kriesemer SK, Pemsl DE (2008) grown in marine and fresh water ponds. Agriculture Recommendation Domains for pond aquacul- and Biology Journal of North America 3: 117-124 ture. Country case study: Development and status of freshwater aquaculture in Malawi. World Fish Osofero SA, Otubusin SO, Daramola JA (2009) Effect of Center Studies and Reviews. No. 1869. The World stocking density on tilapia (Oreochromis niloticus Lin- Fish Center, Penang, Malaysia. 52 pp naeus 1758) growth and survival in bamboo – net cages trial. African Journal of Biotechnology 8: 1322-1325 Sorphea S, Lundh T, Preston TR, Borin K (2010) Effect Pamba, S., Shaghude, W. Y., Muzuka, A. N. N., 2016. of stocking densities and feed supplements on the Hydrodynamic modelling on transport, dispersion growth performance of tilapia (Oreochromis spp.) and deposition of suspended particulate matter in raised in ponds and in the paddy field. Livestock Pangani estuary, Tanzania. In Estuaries: a lifeline of Research for Rural Development 22: 227 ecosystems in the western Indian Ocean, Springer Yan W, Yi-bo C, Yuni-xia Y, Fa-sheng C (2002) Reduced International Publishing AG, Switzerland 141-160 pp growth rate in hybrid tilapia (Oreochromis Mossam- Pauly D (1983) Some simple methods for the assessment bicus x O. Niloticus) at intermediate stocking density. of tropical fish stocks. FAO Fisheries Technical Chinese Journal of Oceanology and Limnology 20: paper, (234), FAO, Rome, Italy. 52 pp 344-347